/**
* Request a sync of the in-memory store back to persisted localStorage.
*
- * This function debounces updates. When called with a flush already pending, the
- * scheduled flush is postponed. The call to localStorage.setItem will be keep
- * being deferred until the page is quiescent for 2 seconds.
+ * This function debounces updates. The debouncing logic should account
+ * for the following factors:
*
- * Because localStorage is shared by all pages from the same origin, if multiple
- * pages are loaded with different module sets, the possibility exists that
- * modules saved by one page will be clobbered by another. The only impact of this
- * is minor (merely a less efficient cache use) and the problem would be corrected
- * by subsequent page views.
+ * - Writing to localStorage is an expensive operation that must not happen
+ * during the critical path of initialising and executing module code.
+ * Instead, it should happen at a later time after modules have been given
+ * time and priority to do their thing first.
+ *
+ * - This method is called from mw.loader.store.add(), which will be called
+ * hundreds of times on a typical page, including within the same call-stack
+ * and eventloop-tick. This is because responses from load.php happen in
+ * batches. As such, we want to allow all modules from the same load.php
+ * response to be written to disk with a single flush, not many.
+ *
+ * - Repeatedly deleting and creating timers is non-trivial.
+ *
+ * - localStorage is shared by all pages from the same origin, if multiple
+ * pages are loaded with different module sets, the possibility exists that
+ * modules saved by one page will be clobbered by another. The impact of
+ * this is minor, it merely causes a less efficient cache use, and the
+ * problem would be corrected by subsequent page views.
*
* This method is considered internal to mw.loader.store and must only
* be called if the store is enabled.
* @method
*/
requestUpdate: ( function () {
- var timer, hasPendingWrites = false;
+ var hasPendingWrites = false;
function flushWrites() {
var data, key;
} );
}
+ // Let the next call to requestUpdate() create a new timer.
hasPendingWrites = false;
}
- function request() {
- // If another mw.loader.store.requestUpdate() call happens in the narrow
- // time window between requestIdleCallback() and flushWrites firing, ignore it.
- // It'll be saved by the already-scheduled flush.
- if ( !hasPendingWrites ) {
- hasPendingWrites = true;
- mw.requestIdleCallback( flushWrites );
- }
+ function onTimeout() {
+ // Defer the actual write via requestIdleCallback
+ mw.requestIdleCallback( flushWrites );
}
return function () {
- // Cancel the previous timer (if it hasn't fired yet)
- clearTimeout( timer );
- timer = setTimeout( request, 2000 );
+ // On the first call to requestUpdate(), create a timer that
+ // waits at least two seconds, then calls onTimeout.
+ // The main purpose is to allow the current batch of load.php
+ // responses to complete before we do anything. This batch can
+ // trigger many hundreds of calls to requestUpdate().
+ if ( !hasPendingWrites ) {
+ hasPendingWrites = true;
+ setTimeout( onTimeout, 2000 );
+ }
};
}() )
}
dépôts / lhc / web / wiklou.git / blobdiff